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mm: thp: set the accessed flag for old pages on access fault

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On x86 memory accesses to pages without the ACCESSED flag set result in
the ACCESSED flag being set automatically.  With the ARM architecture a
page access fault is raised instead (and it will continue to be raised
until the ACCESSED flag is set for the appropriate PTE/PMD).

For normal memory pages, handle_pte_fault will call pte_mkyoung
(effectively setting the ACCESSED flag).  For transparent huge pages,
pmd_mkyoung will only be called for a write fault.

This patch ensures that faults on transparent hugepages which do not
result in a CoW update the access flags for the faulting pmd.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Acked-by: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Ni zhan Chen <nizhan.chen@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Will Deacon 2012-12-11 16:01:27 -08:00 committed by Linus Torvalds
parent eb2db439a3
commit a1dd450bcb
3 changed files with 32 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/huge_mm.h
View File

@ -8,6 +8,10 @@ extern int do_huge_pmd_anonymous_page(struct mm_struct *mm,
extern int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
struct vm_area_struct *vma);
extern void huge_pmd_set_accessed(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long address, pmd_t *pmd,
pmd_t orig_pmd, int dirty);
extern int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pmd_t *pmd,
pmd_t orig_pmd);

22
mm/huge_memory.c
View File

@ -784,6 +784,28 @@ out:
return ret;
}
void huge_pmd_set_accessed(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long address,
pmd_t *pmd, pmd_t orig_pmd,
int dirty)
{
pmd_t entry;
unsigned long haddr;
spin_lock(&mm->page_table_lock);
if (unlikely(!pmd_same(*pmd, orig_pmd)))
goto unlock;
entry = pmd_mkyoung(orig_pmd);
haddr = address & HPAGE_PMD_MASK;
if (pmdp_set_access_flags(vma, haddr, pmd, entry, dirty))
update_mmu_cache_pmd(vma, address, pmd);
unlock:
spin_unlock(&mm->page_table_lock);
}
static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long address,

8
mm/memory.c
View File

@ -3537,8 +3537,9 @@ retry:
barrier();
if (pmd_trans_huge(orig_pmd)) {
if (flags & FAULT_FLAG_WRITE &&
!pmd_write(orig_pmd) &&
unsigned int dirty = flags & FAULT_FLAG_WRITE;
if (dirty && !pmd_write(orig_pmd) &&
!pmd_trans_splitting(orig_pmd)) {
ret = do_huge_pmd_wp_page(mm, vma, address, pmd,
orig_pmd);
@ -3550,6 +3551,9 @@ retry:
if (unlikely(ret & VM_FAULT_OOM))
goto retry;
return ret;
} else {
huge_pmd_set_accessed(mm, vma, address, pmd,
orig_pmd, dirty);
}
return 0;
}